This invention relates to the use of magnetic resonance imaging (MRI) techniques, and more particularly the invention relates to the measurement of blood flow using MRI.
The knowledge of time averaged blood flow is clinically important for diagnosing various vascular-related diseases, and a quick and robust tool for measuring time-averaged blood flow is extremely needed in clinical settings. Phase-contrast (PC) MR imaging can be an accurate tool for measuring time-averaged blood flow rates, information that can be helpful for diagnosing various diseases such as portal venous or pulmonary arterial hypertension. Cardiac gated techniques, such as cine PC can be used to measure time-averaged flow rates from time-resolved data. However, the long scan times, typically several minutes, of cine PC can degrade the accuracy and repeatability due to irregular heart rhythm or respiratory motion. Faster gated methods or real time techniques can provide alternative methods in measuring time-averaged flow rates with shorter scan times. However, the low spatial resolution of these methods limits their clinical applications to relatively large vessels.
Applying a PC pulse sequence without cardiac gating could significantly reduce scan times compared to gated PC methods while achieving sufficient spatial resolution. Ungated PC methods with a two-dimensional Fourier transform (2DFT) trajectory can produce accurate measurements of time-averaged flow rates if the flow is steady or only weakly pulsatile. However, successful applications of these methods can require prior information of the imaging object (e.g., vessels size, flow waveform, and the like) careful selection of the scan perimeters, and scan times inconveniently longer than a breath hold. Moreover, if the flow is strongly pulsatile, these methods cannot repeatedly produce accurate measurements within reasonable scan times.
The present invention is directed to an MR technique for rapidly and robustly measuring time averaged flow rates even in small arteries and in the presence of strong pulsatility.